Clear and orderly summary of Chapter 11 of the book "Genetics: Analysis and Principles, 6th Edition by Robert Brooker". Together with all my other summaries of Genetics I got an 8,5 for this course.
DNA replication; existing DNA strands make new DNA strands
11.1 Structural overview of DNA replication
Double stranded DNA structure is hold together
- Base stacking (op een bepaalde manier op elkaar liggen)
- Hydrogen bonding between the bases
Replication
Two complementary strands come apart and serve a
template strand or parental strand.
Daughter strands; the two newly made strands of
DNA.
new made from 5’ → 3’ on the new strand!! Template strand is thus read from 3’ → 5’
Leading strand; 5’ → 3’ in once a time
Lagging strand; 5’ → 3’ in pieces → Okazaki fragments
Semiconservative is the only model that described replication correct → one parental
strand and one daughter strand
Features (kenmerken) that DNA can be replicated
- Double-stranded structure
- Complementary structure → base paring A+T and C+G
11.2 Bacterial DNA replication: The formation of two replication forks at the
origin of replication
Origin of replication in bacterial; there is only 1, it functions as an initiation site for
proteins that begin the process of DNA replication. (witte bolletje)
The synthesis of new daughter strands is initiated in the origin of replication and
proceeds both directions → bidirectionally
Replication fork; region in which two DNA strands are separated and new strands are
being synthesized. (gele pijltjes)
, Protein that binds to origin of replication
oriC; orginin of chromosomal replication.
Three types of DNA within oriC of an E.coli
- AT-rich region
- DnaA box sequences
- GATC methylation sites
DNA replication
DnaA proteins bind to sequences in 5 DnaA boxes and to each other.
HU and IHF (DNA-binding proteins) cause the DNA to bend around
the complex of DnaA proteins, this results in separation of the strands
at the AT-rich region.
DNA helicase (DnaB protein) binds to the origin. DnaC assist this
process.
DNA helicase separates the DNA in both directions (5’ →3’), creating 2
replications forks
GATC methylation sites
Are involved (betrokken) with regulating DNA replication.
The GATC sites are methylated (addiction of methyl group to a substrate) in both
strands. This full methylation facilitates initiation of DNA replication.
The newly made strands are not methylated because A rather than methyladenine is
incorporated (opgenomen). Initiation of DNA replication does not occur to fast
because the new strands are not fully methylated.
11.3 Bacterial DNA replication: synthesis of new DNA strands
Functions of proteins with DNA replication
DNA helicase (DnaB); separate double stranded DNA
Topoisomerase II (DNA gyrase); removes positive supercoiling
Single-strand binding proteins; prevent from re-forming double stranded structure
Primase; synthesizes RNA primer → needed because DNA polymerase cannot
initiate DNA replication on a bare template strand. It is on the begin of the new
strand. DNA primer is used for PCR
DNA polymerase III; synthesizes daughter strand of DNA
DNA polymerase I; removes RNA primers full gaps with DNA
DNA ligase; links the Okazaki fragments together.
Unwinding of the helix
DNA helicase break the hydrogen bonds and
unwind the strands; this generates positive
supercoiling ahead of each replication fork.
Topoisomerase II relax (verlicht) positive
supercoiling
Then single-binding proteins prevent from re-
forming double stranded structure.
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